The present invention relates generally to chucks and more particularly to a chuck that may be locked or unlocked by rotating the drive shaft of a power tool.
Chucks are well known and are used in many applications. In general, a chuck is connected to the drive shaft of a power tool. One common example of the type of power tool that a chuck may be used on is an electric drill. However, chucks are also used on numerous other tools, such as screw drivers, nut drivers and grinders. Moreover, power tools may be powered by pneumatics, electricity, manual power or by other power sources. Chucks are generally used to grip the shaft of various work tools so that the work tool rotates with the drive shaft of the power tool. Typical types of work tools that may be used with a chuck include drill bits, screwdriver bits and grinding disks or stones.
A wide variety of chucks have been developed. The most common type of chuck that is employed uses three jaws to grip the shaft of a work tool. These types of chucks are able to securely grip shafts with both round and polygonal cross-sections. Typically, the jaws move towards each other in a smaller diametrical relationship as the chuck is tightened and move away from each other in a larger diametrical relationship as the chuck is loosened. Most chucks are designed so that the jaws have a relatively large range of movement. This allows a single chuck to grip many different work tools with different sized shafts.
Typically, chucks also have an adjustment mechanism that is used to tighten and loosen the jaws. Conventional adjustment mechanisms include an adjustment ring that is threaded to the jaws. Thus, when the adjustment ring is rotated, the threaded engagement between the adjustment ring and the jaws causes the jaws to move toward each other or away from each other depending on the direction the adjustment ring is rotated. Commonly, an outer sleeve that the user may operate by hand is provided which is fixedly attached to the adjustment ring. As a result, when the user rotates the outer sleeve in one direction, the jaws move towards each other in a tightening direction. Likewise, when the user rotates the outer sleeve in the opposite direction, the jaws move away from each other in a loosening direction. Other types of engagement structures may also be used. For example, some chucks use a key to rotate a sleeve that is fixedly attached to the adjustment ring. Typically in these chucks, the key engages a ring gear on the sleeve while being radially fixed to the body of the chuck. As a result, the sleeve rotates and threadably moves the jaws as the user rotates the key, thereby providing the user with increased leverage.
In general, however, most chucks that are commercially sold must be manually operated when tightening and loosening the jaws. This may make the use of a chuck time-consuming, since tightening and loosening often involves rotating the adjustment ring numerous times until the jaws are sufficiently tight against the work tool shaft or sufficiently loose to allow the work tool to be removed from the chuck. This may be a particular disadvantage in operations where a user is likely to use several different work tools during a job and may need to change work tools repeatedly. For example, this may be a problem in drilling and screwing jobs where a user needs to drill a number of pilot holes and then drive screws into the pilot holes. This may require numerous work tool changes between drill bits and driver bits during the course of the job. Because many conventional chucks must be manually operated, the time required to finish a job may be longer than desired and the user may tire before the job is done.
Another problem with manually operated chucks is that the user may sometimes fail to fully tighten the chuck. This may cause the jaws to lose their grip on the work tool when the power tool is operated. Usually, this results in the power tool and the chuck spinning around the shaft of the work tool without transferring rotational torque. This can be particularly annoying and inconvenient to a user, especially in the middle of a long job where the user has had to manually change a work tool numerous times. Sometimes a user may also have difficulty loosening a chuck to remove work tools. This may occur when the user overtightens the chuck or may occur due to unintentional tightening during use. This can also be frustrating and may increase the amount of time needed to finish a project.